The present invention relates to an electronically controlled timepiece that controls timepiece hand driving in response to a signal, as a reference, from an oscillator circuit that employs a time standard source such as a crystal oscillator, a power supply control method for the electronically controlled timepiece and a time correction method for the electronically controlled timepiece.
In one of known electronically controlled mechanical timepieces that are controlled by making use of an IC or a crystal oscillator, a generator converts, into electrical energy, mechanical energy released by a mainspring, the electrical energy drives a rotation controller, which controls a current flowing through a coil of the generator, and hands secured to train wheels that transmit the mechanical energy from the mainspring to the generator are accurately driven to indicate accurate time.
Electrical energy from the generator is once stored in a smoothing capacitor, and the power from the capacitor drives the rotation controller. Since the capacitor is supplied with an alternating-current electromotive force in synchronization with the rotation period of the generator, it is not necessary to store power for a long period of time to enable the rotation controller having an IC or a crystal oscillator to operate. Conventionally, a relatively small capacitance capacitor enabling the IC or the crystal oscillator to operate for several seconds, i.e., a capacitor of 10 xcexcF or so is employed.
The electronically controlled mechanical timepiece needs no motor because the mainspring is a power source for driving timepiece hands, and is low cost with a small component count. It is sufficient if a small amount of electrical energy needed to drive an electrical circuit is generated. A small input energy is enough to drive the timepiece.
The electronically controlled mechanical timepiece has the following drawback. When a time correction operation (a timepiece hand setting operation) is performed with the crown pulled out, each of an hour hand, a minute hand, and a second hand is stopped to set an accurate time. The stop of the hands stops train wheels, and thus the generator as well.
The input of the electromotive force to the smoothing capacitor from the generator is suspended, while the IC is continuously driven. The charge stored in the capacitor is discharged to the IC side, and a voltage across terminals of the IC gradually drops. The voltage applied to the IC thus drops below an oscillation stop voltage (Vstop, for instance, 0.6 V), leading to the stop of the rotation controller.
When the oscillation of the IC stops, the power consumption is reduced, and the voltage drop rate in the capacitor also becomes slow. When the time correction operation takes time long enough to cause the voltage of the capacitor to drop below the oscillation stop voltage, the capacitor typically falls to a voltage of 0.3 to 0.4 V slightly lower than the oscillation stop voltage. When the time correction operation (hand setting time) becomes excessively long, to several minutes, for instance, the capacitor is fully discharged with the voltage thereof dropped to zero V.
Even if the generator starts rotating with the crown pushed into after the hand setting, the capacitor, the voltage of which has once dropped below the oscillation stop voltage as a result of discharge, takes time before the capacitor is charged again to be high enough to reach a drive start voltage (voltage capable of driving the IC) for the rotation controller. The IC (an oscillator circuit) remains inoperative throughout, and no accurate time control is performed.
Specifically, when the crown is pulled out to a second step (for a hand setting mode) from a zero step (for a normal hand driving mode) or from a first step (for a calendar correction mode) at time point A as shown in FIG. 26, the rotor of the generator stops, stopping charging a capacitor C1. On the other hand, the capacitor C1 continuously feeds electrical energy to the rotation controller (including a xe2x80x9cdrive ICxe2x80x9d in a drive circuit for driving the crystal oscillator as a time standard source), thereby allowing the crystal oscillator to continuously oscillate.
The voltage of the power source capacitor C1 gradually drops. At time point B1 (within three minutes from time A, for instance), the hand setting operation ends, and the crown is pushed in, moving from the second step to the first step or zero step (for the normal operation). The generator becomes operative again, restarting the charging of the power source capacitor C1, and raising the voltage of the power source capacitor C1. In this case, the oscillation of the crystal oscillator continuously oscillates, the drive circuit (the rotation controller) quickly resumes rotation control of the rotor (brake control), and an indication error subsequent to the hand setting becomes zero.
When the hand setting operation is prolonged to be longer than three minutes, for instance, the voltage of the capacitor C1 drops below the oscillation stop voltage (Vstop, 0.6 V, for instance) of the drive circuit, and the oscillation stops at time B2 at the moment the hand setting operation ends. Even if the crown is moved to the first step at point B2, the rotation controller takes the sum of time T1 and time T2 before it resumes rotation control of the rotor, leading to an indication error.
The time T1 is a duration of time, during which the power source capacitor C1 is charged to a voltage (Vstart) on which the drive circuit and the oscillator circuit in the rotation controller normally operate. The voltage Vstart is typically higher than the voltage Vstop, and is 0.7 V, for instance.
The time T2 is a duration of time from the application of the oscillation start voltage (Vstart) until the oscillator circuit starts oscillating. The time T2 becomes longer as the voltage of the power source capacitor C1 is lower, and ranges from several seconds to several minutes, as shown in FIG. 27. For instance, when the oscillation start voltage (Vstart=0.7 V) is reached with the power source capacitor C1 gradually charged, the time T2 is approximately 20 seconds with the voltage (0.7 V) applied thereto.
When the hand setting operation takes time, the voltage of the power source capacitor C1 drops, thereby stopping the oscillation. Subsequent to the end of the hand setting operation, the oscillator circuit takes time T1+T2 before the start of the oscillation. Because of a lower voltage applied thereto, the oscillator circuit takes several seconds to several minutes for T2 alone. Before the start of the oscillation, the rotation of the rotor is not controlled. The hands gain or lose time, suffering from a substantial indication error.
The use of a large capacitance capacitor C1 to permit a longer hand setting time is contemplated. The oscillator circuit is thus prevented from stopping even if the hand setting takes three minutes or longer.
The use of a large capacitance capacitor slows the rise rate of the power source voltage. When the mainspring is released and stopped, it takes a long time to increase the voltage across the capacitor from the state in which no charge is stored in the power source capacitor. For a long time from the start of tightening of the mainspring to the rise of the power source voltage, the hands remain unable to present accurate time. In this case, there is a possibility that the user may mistake the state for a timepiece failure. Increasing the capacitance of the capacitor is thus not practical.
Increasing the power generation capacity of the generator to complete charging in a short time is contemplated. This arrangement increases the size of the generator, and also needs to increase the size of the mainspring as the torque to be transferred from the mainspring for feeding mechanical energy to the generator increases. This arrangement cannot be adopted for use in wristwatches, which are subject to the limitation of area and thickness dimensions.
In some of a variety of electronically controlled timepieces, such as a self-winding generator timepiece, a solar-cell charging timepiece, a battery driven timepiece, other than the electronically controlled mechanical timepiece, an oscillator circuit or an IC is stopped during a time correction operation to reduce power consumption and to prolong operation time. In this case, it takes several seconds to several minutes for the oscillator circuit to stably operate. A time error is also introduced.
It is an object of the present invention to provide an electronically controlled timepiece, a power supply control method for the electronically controlled timepiece, and a time correction method for the electronically controlled timepiece.
An electronically controlled timepiece of the present invention which includes a power source, an analog circuit driven by the power source, a power supply circuit for a logic circuit arranged in the analog circuit, the logic circuit driven by the output of the power supply circuit therefor, and an oscillator circuit driven by the output of the power supply circuit for the logic circuit. The electronically controlled timepiece further includes a power source switch for suspending the supply of electrical energy to the analog circuit other than the power supply circuit for the logic circuit from the power source during a time correction operation of the electronically controlled timepiece, and clock input limiting means for suspending a clock input from the oscillator circuit to the logic circuit during the time correction operation.
In accordance with the present invention, the power source switch suspends the supply of electrical energy from the power source, such as a capacitor or a battery, to the analog circuit other than the power supply circuit for the logic circuit during the time correction operation (hand setting operation), and the clock limiting means suspends the clock input from the oscillator circuit to the logic circuit. During the hand setting operation, only both the oscillator circuit and the power supply circuit for the logic circuit required to drive the oscillator circuit are driven with the remaining circuits all inoperative. With this arrangement, power consumption during the hand setting operation is reduced. When the capacitance of the capacitor is small, the voltage drop in the power source capacitor is limited during a typical hand setting operation (for instance, 3 to 5 minutes), and the driving of the oscillator circuit is continuously performed. With the oscillator circuit continuously operating during the hand setting operation, a normal control operation is quickly resumed after the hand setting operation, and the indication error at the shifting back from the hand setting operation is eliminated. With the power consumption reduced, there is no need for a large-sized generator, and the present invention is implemented in a wristwatch, which is typically subject to the limitation of area and thickness dimensions.
The power supply circuit for the logic circuit employs a constant voltage regulator.
The electronically controlled timepiece preferably includes logic circuit initializing means for initializing the internal status of the logic circuit during the time correction operation (hand setting operation).
If control information prior to the hand setting operation remains in the logic circuit, governing control of a rotor is not smoothly performed at the shifting back from the hand setting operation, and the time taken before the start of the governing control may be included as an error. In contrast, if the internal status of the logic circuit is initialized when the clock input to the logic circuit is cut off at the hand setting operation, the governing control of the rotor at the shifting back from the hand setting operation is smoothly performed, and the time indication error is reliably eliminated.
An electronically controlled timepiece preferably includes an external control member for setting two-step statuses of a normal mode and a time correction mode, and an external control member detector circuit for detecting the status of the external control member, wherein the external control member detector circuit includes first and second inverters, a first signal line for connecting the output of the first inverter to the input of the second inverter, a second signal line for connecting the output of the second inverter to the input of the first inverter, and a selection switch for connecting a signal input line to one of the first and second signal lines with the external control member in the time correction mode, and for connecting the signal input line to the other of the first and second signal lines with the external control member in the other mode.
A crown detector circuit 100 shown in FIG. 28 has typically been used to detect the pulled status of the external control member such as a crown or a button. For instance, the pulled statuses of the crown of the electronically controlled mechanical timepiece include a normal zero step (in which the mainspring is tightened by turning the crown with the hands turning and the generator generating), a first step (in which a calendar is corrected by turning the crown with the hands turning and the generator generating), and a second step (in which time correction is performed by turning the crown with the rotor stopping moving, the hands motionless, and the generator not generating).
The crown detector circuit 100 includes a switch 101 which is turned on and off depending on the pulled status of the crown, two pull-down resistors 102 and 103, and an inverter 104. The gate of the pull-down resistor 102 is at a voltage VDD (high level), and the pull-down resistor 102 is normally turned on. The gate of the pull-down resistor 103 is connected to the pull-down resistor 102 through the inverter 104. The switch 101 is turned off (open) with the crown in the zero step or the first step, and is turned on with the crown in the second step (closed). When the switch 101 is turned off with the crown in the zero step or the first step, the pull-down resistor 102 is turned on, a voltage VSS, namely, a low-level signal is input to the inverter 104, and the output signal of the inverter 104 is transitioned to a high-level signal. The pull-down resistor 103 receives, at the gate thereof, the high-level signal, thereby turning itself on.
When the switch 101 is turned on with the crown in the second step, the voltage VDD, namely, a high-level signal is input to the inverter 104, and the output of the inverter 104 is transitioned to a low-level signal. As described above, depending on the pulled status of the crown, the crown detector circuit 100 alternates between a xe2x80x9chigh-levelxe2x80x9d, signal and a xe2x80x9clow-levelxe2x80x9d signal.in the output thereof, thereby detecting the position of the crown.
In the conventional crown detector circuit 100, the pull-down resistor 102 is turned on with the crown in the second step, and the pull-down resistor 102 consumes energy. Instead of the crown, a dedicated button is occasionally employed to set the hands. When the hands are set using the external control member, such as the crown or the button, an external control member detector circuit for detecting the status of the external control member has the same construction as that of the crown detector circuit 100, and thus suffers from the same problem.
In contrast, the electronically controlled timepiece having the above-described external control member detector circuit employing the logic circuit almost eliminates energy consumption by the external control member, and therefore substantially reduces power consumption during the hand setting operation.
An electronically controlled timepiece of the present invention preferably includes a mechanical energy source, a generator which is driven by the mechanical energy source, and generates an electromotive force, thereby supplying electrical energy, and a rotation controller, driven by the electrical energy, for controlling the rotation period of the generator.
In the electronically controlled timepiece, the capacitance of the capacitor as the power source is small. The power consumption for the hand setting operation is reduced with the present invention implemented, the time required for the hand setting operation is assured, and the ease of use is attained.
A power supply control method for an electronically controlled timepiece of the present invention, which includes a power source, an analog circuit driven by the power source, a power supply circuit for a logic circuit arranged in the analog circuit, the logic circuit driven by the output of the power supply circuit therefor, and an oscillator circuit driven by the output of the power supply circuit for the logic circuit, includes the step of suspending the supply of electrical energy to the analog circuit other than the power supply circuit for the logic circuit from the power source during a time correction operation of the electronically controlled timepiece, and the step of suspending a clock input from the oscillator circuit to the logic circuit during the time correction operation.
In accordance with the present invention, during the time correction operation of the electronically controlled timepiece, the supply of electrical energy to the analog circuit other than the power supply circuit for the logic circuit from the power source such as a capacitor or a battery is suspended, and the clock input from the oscillator circuit to the logic circuit is suspended. The power consumption during the hand setting operation is reduced. Even with a small capacitance capacitor, the voltage drop in the power source capacitor is limited during a typical hand setting operation (for instance, 3 to 5 minutes), and the driving of the oscillator circuit is continuously performed. At the shifting back from the hand setting operation, a normal control operation is quickly resumed after the hand setting operation, and the time indication error at the shifting back from the hand setting operation is eliminated.
During the hand setting operation of the electronically controlled timepiece, the internal status of the logic circuit is preferably initialized. If the internal status of the logic circuit is initialized when the clock input to the logic circuit is cut off at the hand setting operation, the governing control of the rotor at the shifting back from the hand setting operation is smoothly performed, and the time indication error is reliably eliminated.
An electronically controlled timepiece of the present invention, which includes a mechanical energy source, a generator, driven by the mechanical energy source, for outputting electrical energy, a storage unit for storing electrical energy output by the generator, and a rotation controller, driven by electrical energy supplied by the storage unit, for controlling the rotation period of the generator, includes a power supply control unit for suspending the supply of electrical energy from the storage unit to the rotation controller while the generator stops the operation thereof in response to the time correction operation, and an indication error corrector unit for correcting an error in time indication until the rotation controller resumes a normal operation, when the power supply control unit restarts the supply of electrical energy from the storage unit to the rotation controller in response to the operation of the generator.
In accordance with the present invention, the power supply control unit suspends the supply of electrical energy from the storage unit to the rotation controller when the generator stops the operation thereof during the time correction operation (hand setting operation). Although the oscillator circuit of the rotation controller stops operating, the storage unit is maintained in a charged state during the suspension of the operation of the generator.
Even before the generator fully reaches the operation thereof at the shifting back from the hand setting operation, the storage unit feeds electrical energy to the rotation controller to cause the rotation controller to be fully operative. A time lag prior to the operation of the rotation controller is eliminated, and an error in the time control at the hand setting operation is thus minimized. Since the voltage of the storage unit is maintained at a relatively high level, the time prior to the start of the oscillator circuit of the rotation controller is shortened, and the rotation controller is quickly set to be operative.
With the indication error corrector unit incorporated, the indication error of the hand before the normal operation of the rotation controller is corrected to the extent that the indication error is eliminated or minimized.
The indication error corrector unit may be designed to perform a constant quantity correction corresponding to a predetermined value, or may set a correction value in accordance with a voltage of the storage unit.
The indication error corrector unit may adjust a correction value by detecting temperature.
Specifically, the indication error corrector unit may include a temperature sensor, a voltage detector for measuring a voltage of the storage unit, and a correction value setter for setting a correction value based on values detected by the temperature sensor and the voltage detector.
Since the voltage of the storage unit is maintained at a certain magnitude, the time, which the oscillator circuit, with a certain voltage applied thereto, takes to start oscillation, is substantially constant. By performing a constant quantity correction corresponding to a certain value, the indication error is sufficiently reduced. When a correction value is adjusted by detecting the actual voltage of the storage unit, a highly precise correction is performed to minimize the indication error.
The time prior to the start of the oscillation with the voltage applied to the oscillator circuit varies with temperature as shown in FIG. 16. For this reason, the temperature sensor included in the electronically controlled timepiece measures temperature in the vicinity of the oscillator circuit, and the correction value is adjusted in accordance with the measured temperature. A more precise correction is thus performed. The indication error, under high temperature conditions or low temperature conditions, is thus further minimized.
The power supply control unit preferably includes a switch which is connected in series with the storage unit and is closed while the generator is running, and is opened while the generator is not running.
An electrical switch is acceptable as the switch, but a mechanically driven switch is preferable. When the electrical switch is used, the supply of power may be occasionally not completely blocked. In such a case, as well, a mere leakage current (1 nA) of a silicon diode constituting the electrical switch is discharged. The switch cutoff effect of the switch is almost identical to that of the mechanically driven switch. The use of the mechanically driven switch is preferable from the standpoint of the fully cutting off the supply of power.
The switch is preferably a mechanically driven switch that is opened when a crown remains pulled out to a time correction (hand setting) mode, and is closed when the crown is pushed into to a normal mode. With the switch opened and closed in response to the operation of the crown, the switch is interlocked with the hand setting operation.
A second storage unit (a second capacitor) is preferably connected in parallel with the storage unit. With the second storage unit arranged, power is continuously fed by the second storage even if the timepiece suffers from a mechanical shock, with the switch chattering. This arrangement prevents the rotation controller from being shut down by the chattering.
A time correction method for an electronically controlled timepiece, which includes a mechanical energy source, a generator, driven by the mechanical energy source, for outputting electrical energy, a storage unit for storing electrical energy output by the generator, and a rotation controller, driven by electrical energy supplied by the storage unit, for controlling the rotation period of the generator, includes the step of suspending the supply of electrical energy from the storage unit to the rotation controller during a time correction operation of the electronically controlled timepiece, and the step of correcting an error in time indication until the rotation controller resumes a normal operation when the supply of electrical energy from the storage unit to the rotation controller is restarted at the end of the time correction operation.
At the end of the time correction operation, the indication error may be corrected by a constant quantity correction corresponding to a predetermined value or may be corrected by a correction value set in response to the voltage of the storage unit. At the end of the time correction operation, temperature may be detected, and the correction value may be adjusted in accordance with the detected temperature.
In accordance with the present invention, the power supply control unit suspends the supply of electrical energy from the storage unit to the rotation controller when the generator stops the operation thereof during the time correction operation. The storage unit is maintained in a charged state during the suspension of the operation of the generator. Immediately subsequent to the shifting back from the time correction operation, the storage unit feeds electrical energy to the rotation controller to cause the rotation controller to be operative. Since the applied voltage is maintained at a relatively high level, the rotation controller is quickly set to be operative, and the indication error subsequent, to the time correction operation is reduced.
Furthermore, since the indication error is corrected in accordance with the voltage value of the storage unit and temperature, the indication error of the hands prior to the normal operation of the rotation controller is corrected. The indication error is thus eliminated.
An electronically controlled timepiece of the present invention, which includes a mechanical energy source, a generator, driven by the mechanical energy source, for outputting electrical energy, and a rotation controller, driven by electrical energy, for controlling the rotation period of the generator, includes a main storage unit for storing electrical energy supplied by the generator to drive the rotation controller, an auxiliary storage unit connected in parallel with the main storage unit through a mechanically driven switch that is interlocked with a time correction operation, and a charge control circuit, arranged between the main storage unit and the auxiliary storage unit, for adjusting charging currents to the main storage unit and the auxiliary storage unit, and a direction and a magnitude of a current flowing between the main storage unit and the auxiliary storage unit.
The charge control circuit preferably makes the charging current (charge quantity) to the auxiliary storage unit smaller than the charging current (charge quantity) to the main storage unit when the mechanically driven switch is closed to charge the main storage unit and the auxiliary storage unit with electrical energy from the generator, and allows the auxiliary storage unit to charge the main storage unit when the voltage of the auxiliary storage unit is higher than the voltage of the main storage unit.
Since the present invention includes the auxiliary storage unit that is disconnected from the main storage unit and the generator by the mechanically driven switch, the auxiliary storage unit is maintained in a charged state even when the generator stops the operation thereof during the time correction operation (hand setting operation) in the middle of the normal hand driving. Even if the terminal voltage across the main storage unit drops below the voltage capable of driving the rotation controller at the shifting back from the hand setting operation, a current flows from the auxiliary storage unit to the main storage unit with the mechanically controlled switch closed. With its voltage increased, the main storage unit drives the rotation controller, and a time lag prior to the operation of the rotation controller is eliminated, and an error in the time control at the hand setting operation (an error in the time indication subsequent to the time correction operation) is thus minimized.
When the hand setting operation takes time, when the timepiece has been left unattended for a long period of time to the degree that the terminal voltage across the auxiliary storage unit drops as a result of a self-discharge, the mechanically driven switch is closed to allow a current to flow from the generator to each storage unit. In this case, the charge control circuit for adjusting the direction and the magnitude of the current makes the charging current to the main storage unit larger than the charging current to the auxiliary storage unit, and the main storage unit is charged to be high enough to quickly drive the rotation control circuit. Even after the timepiece has been left unattended for a long period of time, the rotation controller is quickly driven. An error due to a time lag prior to the start of the driving of the rotation controller is reduced, and an error in the time control during the hand setting operation is minimized.
The present invention thus assures both the startup capability subsequent to the hand setting and the accuracy of the hand setting at the same time.
Preferably, the charge control circuit composed of a passive element only is used to control the charging and discharging between the main storage unit and the auxiliary storage unit. The use of the charge control circuit composed of the passive element reduces power consumption and the generation capacity of the generator, compared to the arrangement in which a comparator, i.e., an active element, is used.
When the charging and discharging are controlled between the two storage units (such as capacitors), i.e., the main storage unit and the auxiliary storage unit, the control of the charging and discharging of the capacitor is typically performed by detecting the voltage of each capacitor using a comparator, and by using the output of the comparator to cause a switch circuit, composed of transistors, to operate. In such a timepiece, the comparator is an active element, and the comparator needs power to detect the voltage. The power consumption thus increases.
In a system, such as this timepiece, in which the generation capacity is extremely small, the generation capacity of the generator needs to be increased from a current level to supply power to the comparator. To increase the generation capacity of the generator, means for increasing torque or increasing the size of the generator itself may be contemplated.
In the former means, increasing the energy supply from the mainspring allows the mainspring to fast release. The duration of time of the releasing of the mainspring from the fully tightened position thereof is shortened. In the latter means, the size of the generator becomes large, presenting difficulty in the layout of components in a timepiece that has a limited space available. As a result, the size of the timepiece itself is increased.
Since the present invention includes the charge control circuit having the passive element, the power consumption thereof is small, compared to the arrangement in which the comparator, as an active element, is employed. A generator having a small generation capacity thus works.
The capacitance of the main storage unit is preferably set to be equal to or lower than the capacitance of the auxiliary storage unit. With this arrangement, the voltage of the main storage unit is rapidly increased by allowing the current to f low from the auxiliary storage unit when the main storage unit is discharged. The drive circuit, driven by the main storage unit, is also rapidly driven.
Preferably, the mechanically driven switch is opened during the time correction operation, and is closed at the end of the time correction.
With this arrangement, the auxiliary storage unit is reliably cut off from the rotation controller with the generator stopped during the time correction operation (hand setting operation), and the auxiliary storage unit keeps the charged state thereof for a long period of time, and a long hand setting time is thus permitted.
The charge control circuit preferably includes a resistor and a diode connected in parallel with the resistor, wherein the diode is configured with the reverse direction thereof aligned with the direction of a current charging the auxiliary storage unit from the generator and the forward direction thereof aligned with the direction of a current of the auxiliary storage unit charging the main storage unit.
When the generator charges each storage unit in this arrangement, a current flows through the auxiliary storage unit via the resistor connected in parallel with the diode. The charge quantity to the main storage unit and to the auxiliary storage unit is controlled by the resistance of the resistor. For instance, the use of a resistor having a high resistance as large as 100 Mxcexa9 allows less current to flow to the auxiliary storage unit and more current to flow to the main storage unit, thereby rapidly charging the main storage unit. By setting an appropriate resistance to the resistor, the charge quantity to the main storage unit is controlled.
At the time of the shifting back from the hand setting operation, the charging of the main storage unit by the auxiliary storage unit is performed through the diode with a small charging loss involved therein, compared to the charging performed through the resistor.
The charge control circuit may include a diode only having a reverse leakage current, and wherein the diode is configured with the reverse direction thereof aligned with the direction of a current charging the auxiliary storage unit from the generator and the forward direction thereof aligned with the direction of a current of the auxiliary storage unit charging the main storage unit.
With this arrangement, a small reverse leakage current of the diode is fed to the auxiliary storage unit when each storage unit is charged with the generator. For this reason, less current flows to the auxiliary storage unit, while more,current flows to the main storage unit.
At the time of shifting back from the hand setting operation, the charging current from the auxiliary storage unit to the main storage unit is aligned with the forward direction of the diode, and the voltage drop and charging loss therethrough are thus reduced.
Furthermore, if the charging control circuit is constructed of a diode only, the component count of the charging control circuit, and thus of the timepiece, becomes smaller, leading reduced manufacturing costs.
The charge control circuit may include a resistor and a one-way element connected in parallel with the resistor, wherein the one-way element is configured to cut off a current flowing in a direction to charge the auxiliary storage unit from the generator and to conduct a current of the auxiliary storage unit flowing in a direction to charge the main storage unit. In this case, the one-way element may be a diode having no reverse leakage current.
As in the charge control circuit constructed of the diode and the resistor in parallel connection, the generator charges each of the storage units, and the auxiliary storage unit is charged through the resistor so that the charge quantity to the main storage unit is large for rapid charging. When the auxiliary storage unit charges the main storage unit, the charging is performed through the one-way element, and a charging loss to the main storage unit is minimized.
When the one-way element, such as a diode having no reverse leakage current, allowing currents flowing therethrough in one direction only, is used, an error in the charge quantity due to the reverse leakage current is not created. The charging current is thus precisely controlled.
An electronically controlled timepiece preferably includes an indication error corrector unit for correcting an error in time indication until the rotation controller resumes a normal operation when the supply of electrical energy of the main storage unit to the rotation controller is restarted with the mechanically driven switch closed.
With the indication error corrector unit incorporated, the time indication error until the rotation controller resumes the normal operation is corrected, and the indication error is eliminated or minimized.
In this case, again, the indication error corrector unit may be designed to perform a constant quantity correction corresponding to a predetermined value, or may set a correction value in accordance with a voltage of the storage unit. Furthermore, the indication error corrector unit may adjust a correction value by detecting temperature. More specifically, the indication error corrector unit may includes a temperature sensor, a voltage detector for measuring a voltage of the storage unit, a correction value setter for setting a correction value based on values detected by the temperature sensor and the voltage detector.
A power supply control method for an electronically controlled timepiece of the present invention which includes a mechanical energy source, a generator, driven by the mechanical energy source, for outputting electrical energy, and a rotation controller, driven by electrical energy, for controlling the rotation period of the generator, includes the step of arranging a main storage unit which stores electrical energy supplied by the generator to drive the rotation controller and connecting an auxiliary storage unit in parallel with the main storage unit through a mechanically driven switch, the step of opening the mechanically controlled switch during a time correction operation of the electronically controlled timepiece, and the step of flowing a current from the auxiliary storage unit to the main storage unit to charge the main storage when the voltage of the auxiliary storage unit is higher than the voltage of the main storage unit with the mechanically driven switch closed at the end of a time correction operation, and the step of making a charging current supplied from the generator to the main storage unit greater than a charging current supplied from the generator to the auxiliary storage unit when the voltage of the auxiliary storage unit is not higher than the voltage of the main storage unit.
In this arrangement as well, the main storage unit is charged to be high enough to quickly drive the rotation control circuit at the shifting back from the hand setting operation and an error due to a time lag before the start of the driving of the rotation controller is reduced, and an error in the time control during the hand setting operation (an error in the time indication subsequent to the time correction operation) is minimized.
Even after the timepiece has been left unattended for a long period of time, the rotation controller is quickly driven. An error due to a time lag before the start of the driving of the rotation controller is reduced, and an error in the time control during the hand setting operation is minimized. The present invention thus assures both the startup capability subsequent to the hand setting and the accuracy of the hand setting at the same time.